CE 3500 Transportation Engineering Horizontal curve examples April

CE 3500 Transportation Engineering Horizontal curve examples April 1, 2011

ANNOUNCEMENTS

Homework 4 due Wednesday No lab next week either; Dr. Jim Kladianos will be speaking in lab April 14.

REVIEW

Assorted formulae PI T D/2 PC D E M PT C D R Curve length

Final answer: Station 238+44. 75 239+00 240+00. . . 252+00 252+30. 17 Deflection angle 0 1° 6'18" 3° 6'18". . . 27° 6'18" 27° 42'30" Chord length (ft) 0 55. 25 99. 98. . . 99. 98 30. 17

EXAMPLE

You are designing a curve with a 2000 -ft radius. If the tangent length is 400 ft, and PI is at station 103+00, what is the station of PT? PI T D/2 PC D E M C D R

SIGHT DISTANCE CONSIDERATIONS

Where does sight distance come into play for a curve? PI D E T PC D/2 M C D

Idea: consider a segment of the curve as long as the necessary sight distance; find the corresponding middle ordinate length. SS D M D

Idea: consider a segment of the curve as long as the necessary sight distance; find the corresponding middle ordinate length. SSD M D

EXAMPLE

A horizontal curve on a level two-lane highway with 12 -ft. lanes has a 2000 ft. radius, and a 60 mph design speed. Coefficient of braking friction is 0. 28. What distance must be cleared from the inside edge of the inside lane? SSD M Why did I give you the number of lanes and lane width? D

FANCY CURVES

Compound curves: two or more horizontal curves in the same direction

Reverse curves: two or more horizontal curves in opposite direction (often equal radii).

Spiral curves: radius changes during the curve. Often used as a transition between curves and straight segments.